Re: [patch 02/18] hugetlb: factor out huge_new_page

[Christoph Lameter <clameter@sgi.com>]

On Fri, 25 Apr 2008, Nishanth Aravamudan wrote:

> > >>> This happens to fix a minor bug. When alloc_bootmem_node returns
> > >>> a fallback node on a different node than passed the old code
> > >>> would have put it into the free lists of the wrong node.
> > >>> Now it would end up in the freelist of the correct node.
> > >> This is rather frustrating. The whole point of having the __GFP_THISNODE
> > >> flag is to indicate off-node allocations are *not* supported from the
> > >> caller... This was all worked on quite heavily a while back.
> > 
> > Perhaps it was, but the result in hugetlb.c was not correct.
> 
> Huh? There is a case in current code (current hugepage sizes) that
> allows __GFP_THISNODE to go off-node?

Argh. Danger. SLAB will crash and/or corrupt data if that occurs.

> > No, the bug is already there even without the bootmem patch.
> 
> Where does alloc_pages_node go off-node? It is a bug in the core VM if
> it does, as we decided __GFP_THISNODE semantics with a nid specified
> indicates *no* fallback should occur.

But this is only for bootmem right? SLAB is not using bootmem so we could 
make an exception there. The issue is support of __GFP_THISNODE in the 
bootmem allocator?



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